Polyamides from xylylene diamines and 5-t-butylisophthalic acids



United States Patent 3,426,001 POLYAMIDES FROM XYLYLENE DIAMINES AND S-t-BUTYLISOPHTHALIC ACIDS James S. Ridgway, Durham, N.C., assignor to Monsanto Company, St. Louis, Mo., a corporation of Delaware N0 Drawing. Filed Dec. 29, 1966, Ser. No. 605,576 US. Cl. 260--78 3 Claims Int. Cl. C08g 41/02 ABSTRACT OF THE DISCLOSURE Copolyamides are produced from hexamethylene diamine, adipic acid, xylylene diamine and 5 -t-butylisophthalic acid. These polyamides are useful in the production of shaped articles, and particularly in the production of textile fibers and reinforcing cords.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to copolyamides produces from dicarboxylic acids and diamines.

Description of the prior art Polyamides, such as polyhexamethylene adipamide (nylon 66) and polycaproamide (nylon 6) are well known in the art and have found significant commercial success both as textile fibers and as reinforcing fibers, such as the cord. Although the textile fibers obtained from the previously known fiber-forming polyamides heretofore known are of great value, much research effort is being continuously expended in order to improve their properties. For example, previously known polyamides are opaque in appearance. In some commercial uses, for example, packing material and fishing lines, it is desirable that the polyamide textile fibers be transparent. Furthermore, while, as pointed out above, previously known polyamides have been significant use in the reinforcement of rubber articles such as vehicle tires, an inherent draw back in their use to reinforce vehicle tires in their tendency to flatspot. Flatspotting is a term used to describe the out-of-roundness that occurs when a polyamide reinforced vehicle tire is allowed to rest for a period of time. That portion of the tire which is in contact with the pavement becomes flattened and, when the vehicle is started again this fiat spot causes vibration of the vehicle. While this phenomena of flatspotting is not completely understood, it is thought that it is related to heat and moisture stability. There is, therefore, at present a great deal of effort being put into finding polyamides which have increased heat and moisture stability.

SUMMARY OF THE INVENTION The copolyamides of the present invention are useful in the production of shaped articles by extrusion, molding or casting in the nature of yarns, fabrics, films, pelh'cles, bearings, ornaments or the like. They are particularly useful in the production of textile fibers and as reinforcing cords produced therefrom.

The present invention provides a novel fiber-forming copolyamide composed of (A) 70 to 98 mole percent, based on the molecular weight of the copolyamide, of units represented by the structure Patented Feb. 4, 1969 In a typical preparation the copolyamide is formed by interpolyrnerizing the desired proportions of adipic acid, hexamethylene diamine, xylylene diamine and S-t-butylisophthalic acid. The acids and diamines may be added to the polymerization step as such or, as is preferred, they may be added in the form of salts prepared from one of the acids and one of the diamines. In any event, the amount of each component added to the polymerizer is determined by the amount desired in the copolymer product. Generally, the amounts of xylylene diamine and 5-t-butylisophthalic acid added to the polymerization step is sufiicient to provide from 2 to 30 mole percent in the copolymer of units having the structure It has been found that at least about 2 mole percent is needed in order that the advantageous effects be realized. Amounts greater than 30 mole percent are usually to be avoided since the tenacity and melting point of the copolymer are adversely affected. The preferred amount of these units is between 5 and 20 mole percent.

The copolyamides of this invention are prepared by procedures well known in the art and commonly employed in the manufacture of simple polyamides. That is, the reactants are heated at a temperature of from 180 C. to 300 C. and preferably from 200 C. to 295 C. until the product has a sufiiciently high molecular weight to exhibit fiber-forming properties, which properties are reached when the copolyamide has an intrinsic viscosity of at least 0.4. The reaction can be conducted at superatmospheric, atmospheric, or subatmospheric pressure. Often it is desirable, especially in the last stage of the reaction, to employ conditions, e.g. reduced pressure, which will aid in the removal of the reaction by-products. Preferably, the reaction is carried out in the absence of oxygen, for example, in an atmosphere of nitrogen.

Intrinsic viscosity as employed herein is defined as C Lim C (1 in which 7 is the relative viscosity of a dilute solution of the polymer in m-cresol in the same units at the same temperature and C is the concentration of grams of polymer per cc. of solution.

The xylylene diamine employed in producing the copolymers of the present invention may be either the metaor para-isomer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS I In Examples 14 copolymers were prepared having the indicated mole percent of components. (66 represents hexamethylene adipamide units and MXD-TBIA represents units from meta-xylylene diamine and S-t-butylisophthalic acid.) In each example the amount of each component employed was determined by its desired mole percentage in the copolymer. Salts of (1) hexamethylene diamine and adipic acid, (2) hexamethylene diamine and S-t-butylisophthalic acid and (3) meta-xylylene diamine and adipic acid were dissolved in water and the resulting solution was placed in a stainless steel, high pressure autoclave which had been previously purged with nitrogen. The temperature and pressure within the autoclave were slowly raised until values of 220 C. and 250 p.s.i.g. respectively, were reached. The temperature was then further increased to 243 C. while the pressure was maintained at 250 p.s.i.g. by removal of steam condensate. The pressure was then gradually reduced to atmospheric over a 25-minute period. The temperature was allowed to level at 280 C. and the polymer allowed to equilibrate for 30 minutes. The polymer was melt spun directly from the bottom of the autoclave to yield a mono-filament yarn having good textile properties. The increased stability to heat and moisture was demonstrated by the percent retention of sonic modulus at rising temperatures, as shown in Table I and Table H.

TABLE I RH) Mole percent, Mole percent, Sonic Ex. 66 MX modulgs at I claim:

1. A linear, fiber-forming, completely transparent copolyamide consisting of (A) 70 to 90 mole percent based on the molecular weight of the copolyamide of units represented by the structure 1 I I] ll -N( 2)a-N 2)4C- (B) 30 to mole percent based on the molecular weight of the copolyamide of units represented by the structure 2. The linear, fiber-forming, completely transparent copolyamide as defined in claim 1 wherein component (A) Percent retained at- TBIA 50 0. 80 0. 110 0. 130 0. 150 0.

TABLE H (30% RH) consists of 90 to 80 mole percent and component (B) con- 35 sists of 10 to 20 mole percent of the copolyamide. Percent tamed 3. A textile fiber of the copolyamide of claim 1. 0. C. 0. C.

References Cited 83 70 57 4s 90 1 5 57 40 UNITED STATES PATENTS 3g 32 23 9% 2,554 8/1941 Carothers 260--78 2,918,454 12/1959 Graham 26078 The results shown in Tables I and II conclusively indi- ,620 8/ 1955 Carlston et a1 260-78 cate that the copolyamides of the present invention are 21 10/ 1956 Lum et a1. 260-78 for superior, in regard to their heat and moisture sta- 45 ,994 12/1961 Bell et a1. 260-78 bility, than the conventional nylon 66. Furthermore, while the polyamide of Example 1 above was opaque in appearance, those of Examples 2-4 were completely transparent. As stated above, polyamides which are transparent find many commercial uses for which conventional, opaque polyamides are not suitable.

US. Cl. X.R. 

